According to the lawsuit filed Wednesday in Denver District Court, four of the couples applied for marriage licenses in Denver in recent days, one pair on Valentine’s Day. The other five married in states where such unions are legal but live in Colorado, where “their valid marriages are reduced to second-class and unequal civil unions, which do not afford them the same rights, protections and security as marriage,” the lawsuit says.

Another unmarried couple filed a similar lawsuit in October in Adams County.

Colorado voters approved a constitutional amendment outlawing gay marriage in 2006. In 2013, the state assembly passed a same-sex civil-unions law. Don Quick, a Democrat running for Colorado attorney general, put a spotlight on the issue last week, challenging the Republican who now holds the office, John Suthers, to stop defending the ban.

“We will defend against this new lawsuit as we would any other,” Suthers said in a statement, noting it was his duty as attorney general to champion state law. “That said, this is an important issue that ultimately the appellate courts will resolve.”

The Denver official responsible for issuing marriage licenses, Debra Johnson, issued a statement Wednesday saying she supported equal treatment for all, but “as an elected official, under oath I am sworn to uphold the law as written, even when those laws are in direct conflict with my personal beliefs.”

Johnson was named as a defendant in the lawsuit filed Wednesday along with Gov. John Hickenlooper.

Last summer, the U.S. Supreme Court struck down a measure of the Defense of Marriage Act denying gay married couples the federal benefits and privileges heterosexual couples have.

Among the plaintiffs in the Colorado lawsuit are Tommy Craig, a middle school administrator, and Joshua Wells, an aerospace engineer, the first couple to enter into a civil union in Arapahoe County. They say in the lawsuit they paid an additional $100 to have their union certified by a judge because of doubts about whether other states would recognize their relationship.

In a statement Wednesday, Nathan Woodliff-Stanley, executive director of the American Civil Liberties Union of Colorado, said his organization has worked for decades on this issue across the United States.

“We recognize the courage and resolve of these couples and their attorneys as they pursue, through the courts, the freedom to marry that all Coloradans deserve,” he said.

The plaintiffs and their lawyers declined to comment beyond Wednesday’s court filing.